Electron micrograph of a biofilm that formed on the inside of a contact lens case.
Ooze. Slime. Gunk. These are just a few of the terms you might use to describe a microbial biofilm. To us, biofilms are just slimy coatings on objects, sometimes helpful, sometimes a nuisance. But to microbes, biofilms are home. Not just home, but the perfect neighborhood, a safe, friendly place where they can put down roots, interact with others, share food and conversation, etc. Bacteria, algae and fungi all can form biofilms.
One of the most interesting things about biofilms is how all the different microbes in them manage to communicate with each other. After all, microbes don't have mouths and vocal cords like we do. Instead of using vibrations of air to communicate like us, they use a chemical language. Microbes make and send out various chemicals that signal to bugs that receive them to do certain things. For example, the message might be, "hey, there's a lot of food over here!" prompting the receiving microbes to move closer to that spot. Or the message might be "y'know, there are enough of us here to form a cozy little biofilm." This type of message, one that tells bacteria how many of them are grouped together, is called quorum-sensing. You'll see this term in the article. A quorum is the minimum number of members of a group that have to be present to make something happen.Another interesting thing about biofilms is the layer of slime that covers them. This slime is made up of water and chemicals technically called polysaccharides <polly-sack-uh-rides>. The polysaccharides are made by certain kinds of microbes, the ones who get biofilms started. The slime layer traps nutrients, anchors members of the biofilm and protects them. Some of the problems for humans caused by this protective effect are described in the article.
Be sure to try the Microbial Slime activity in the Experiments section. You'll get to grow and examine your own slimy microbial neighborhoods.
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